KR101328961B1  Method For Transmitting And Receiving Signals In OpenLoop Spatial Multiplexing Mode  Google Patents
Method For Transmitting And Receiving Signals In OpenLoop Spatial Multiplexing Mode Download PDFInfo
 Publication number
 KR101328961B1 KR101328961B1 KR1020080080461A KR20080080461A KR101328961B1 KR 101328961 B1 KR101328961 B1 KR 101328961B1 KR 1020080080461 A KR1020080080461 A KR 1020080080461A KR 20080080461 A KR20080080461 A KR 20080080461A KR 101328961 B1 KR101328961 B1 KR 101328961B1
 Authority
 KR
 South Korea
 Prior art keywords
 matrix
 precoding
 base station
 signal
 open
 Prior art date
Links
 239000011159 matrix materials Substances 0 abstract claims description 173
 230000000875 corresponding Effects 0 abstract claims description 33
 238000004891 communication Methods 0 claims description 10
 230000035611 feeding Effects 0 claims description 6
 239000004452 animal feeding substances Substances 0 claims description 3
 238000000034 methods Methods 0 description 19
 230000001965 increased Effects 0 description 6
 230000001702 transmitter Effects 0 description 6
 230000000051 modifying Effects 0 description 5
 238000000819 phase cycle Methods 0 description 5
 238000004088 simulation Methods 0 description 5
 239000010410 layers Substances 0 description 4
 230000004301 light adaptation Effects 0 description 2
 239000000047 products Substances 0 description 2
 230000001603 reducing Effects 0 description 2
 230000003935 attention Effects 0 description 1
 239000011162 core materials Substances 0 description 1
 230000003111 delayed Effects 0 description 1
 238000005516 engineering processes Methods 0 description 1
 238000005562 fading Methods 0 description 1
 230000000670 limiting Effects 0 description 1
 239000000203 mixtures Substances 0 description 1
 238000010295 mobile communication Methods 0 description 1
 230000011664 signaling Effects 0 description 1
 238000006467 substitution reaction Methods 0 description 1
Images
Classifications

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04B—TRANSMISSION
 H04B7/00—Radio transmission systems, i.e. using radiation field
 H04B7/02—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas
 H04B7/04—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
 H04B7/0413—MIMO systems
 H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
 H04B7/0486—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking channel rank into account

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04B—TRANSMISSION
 H04B7/00—Radio transmission systems, i.e. using radiation field
 H04B7/02—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas
 H04B7/04—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
 H04B7/06—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
 H04B7/0613—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
 H04B7/0667—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of delayed versions of same signal
 H04B7/0671—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of delayed versions of same signal using different delays between antennas

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04B—TRANSMISSION
 H04B7/00—Radio transmission systems, i.e. using radiation field
 H04B7/02—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas
 H04B7/04—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
 H04B7/06—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
 H04B7/0613—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
 H04B7/0682—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission using phase diversity (e.g. phase sweeping)

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04B—TRANSMISSION
 H04B7/00—Radio transmission systems, i.e. using radiation field
 H04B7/02—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas
 H04B7/04—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
 H04B7/06—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
 H04B7/0613—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
 H04B7/0615—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
 H04B7/0619—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
 H04B7/0621—Feedback content
 H04B7/0634—Antenna weights or vector/matrix coefficients

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04B—TRANSMISSION
 H04B7/00—Radio transmission systems, i.e. using radiation field
 H04B7/02—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas
 H04B7/04—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
 H04B7/06—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
 H04B7/0613—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
 H04B7/0615—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
 H04B7/0619—Diversity systems; Multiantenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
 H04B7/0636—Feedback format
 H04B7/0639—Using selective indices, e.g. of a codebook, e.g. predistortion matrix index [PMI] or for beam selection

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L25/00—Baseband systems
 H04L25/02—Details ; Arrangements for supplying electrical power along data transmission lines
 H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks ; Receiver end arrangements for processing baseband signals
 H04L25/03891—Spatial equalizers
 H04L25/03898—Spatial equalizers codebookbased design

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L27/00—Modulatedcarrier systems
 H04L27/26—Systems using multifrequency codes
 H04L27/2601—Multicarrier modulation systems
 H04L27/2626—Arrangements specific to the transmitter
Abstract
Description
The following description relates to a multiantenna (MIMO) mobile communication system, and more particularly, to a method for efficiently transmitting and receiving signals in an open loop spatial multiplexing mode.
Recently, due to the generalization of information and communication services, the appearance of various multimedia services, and the emergence of high quality services, the demand for fast wireless communication services is rapidly increasing. To cope with this actively, the capacity of the communication system must be increased.In order to increase the communication capacity in the wireless communication environment, a method of finding new available frequency bands and increasing the efficiency of limited resources can be considered. have. Among them, the transceiver is equipped with a plurality of antennas to secure additional spatial area for resource utilization, thereby obtaining diversity gain, or transmitting data in parallel through each antenna to increase transmission capacity. The socalled multiantenna transmit and receive technology has recently been actively developed with great attention.
Among such multiple antenna transmission / reception techniques, a multiinput multipleoutput (MIMO) system using Orthogonal Frequency Division Multiplexing (OFDM) will be described as follows.
1 is a diagram illustrating a general structure of a multiantenna transmission and reception system using OFDM.
In the transmitting end, the channel encoder 101 attaches redundant bits to the transmitted data bits to reduce the influence of the channel or noise, and the mapper 103 converts the data bit information into data symbol information, and the serialparallel converter. 105 parallelizes the data symbols onto a plurality of subcarriers, and the multiantenna encoder 107 converts the parallelized data symbols into spacetime signals. The multiple antenna decoder 109, the paralleltoserial converter 111, the demapper 113, and the channel decoder 115 at the receiving end are the multiple antenna encoder 107, the serialtoparallel converter 105, the mapper ( 103 and the reverse function of the channel encoder 101, respectively.
In a multiantenna OFDM system, various techniques are required to increase data transmission reliability. Among them, a spacetime code (STC) scheme and a cyclic delay diversity scheme are used to increase the spatial diversity gain. Diversity (CDD) and the like, and techniques for increasing the signaltonoise ratio (SNR) include beamforming (BF) and precoding. Here, spacetime code and cyclic delay diversity are mainly used to increase transmission reliability of an open loop system in which feedback information is not available at a transmitter, and beamforming and precoding are applicable in a closed loop system in which feedback information is available at a transmitter. It is used to maximize the signal to noise ratio through the feedback information.
Among the abovedescribed techniques, a technique for increasing the spatial diversity gain and a technique for increasing the signaltonoise ratio, in particular, look at cyclic delay diversity and precoding as follows.
Cyclic Delay Diversity (CDD) technique is to obtain frequency diversity gain at the receiving end by transmitting all signals with different delay or different size in transmitting OFDM signals in a system having multiple transmit antennas. .
2 illustrates a configuration of a transmitting end of a multiple antenna system using a CDD technique.
OFDM symbols are separately transmitted to each antenna through a serialtoparallel converter and a multiantenna encoder, and then a Cyclic Prefix (CP) is attached to the receiver to prevent interference between channels. In this case, the data sequence transmitted to the first antenna is transmitted to the receiver as it is, but the data sequence transmitted to the next antenna is cyclically delayed by a certain sample compared to the antenna of the previous sequence.
On the other hand, if the cyclic delay diversity scheme is implemented in the frequency domain, the cyclic delay can be expressed as a product of a phase sequence.
FIG. 3 is a diagram for describing a method of implementing the CDD technique in the frequency domain as shown in FIG. 2.
As shown in FIG. 3, the data sequence in the frequency domain may be multiplied by a predetermined phase sequence (phase sequence 1 to phase sequence M) set differently for each antenna, and then may be transmitted to the receiver by performing fast inverse Fourier transform (IFFT). This is called a phase shift diversity technique.
Using the phase shift diversity technique, a flat fading channel can be transformed into a frequency selective channel, and frequency diversity gain can be obtained through channel codes or multiuser diversity gain can be obtained through frequency selective scheduling. have.
Precoding schemes include a codebook based precoding scheme used when the feedback information is finite in a closed loop system, and a method of quantizing and feeding back channel information. In the codebookbased precoding, a signaltonoise ratio (SNR) gain is obtained by feeding back the index of a precoding matrix already known to the transmitting and receiving end to the transmitting end.
4 is a block diagram of a transmitter / receiver of a multiantenna system using codebook based precoding.
Here, the transmitting end and the receiving end each have a finite precoding matrix ( P _{1).} _{ } ~ P _{L} ), and the receiver feeds back the optimal precoding matrix index ( l ) to the transmitter using channel information, and the transmitter sends the precoding matrix corresponding to the fed back index to the transmission data ( χ _{1} ~ χ _{Mt} _{)} can be applied.
The phase shift diversity scheme or the CDD scheme may have different requirements in the openloop and closedloop schemes depending on whether feedback information is required. That is, it may be desirable to use different precoding matrices according to the open loop CDD scheme or the closed loop CDD scheme.
Under this assumption, it is necessary to select a suitable precoding matrix so as to obtain sufficient frequency diversity gain according to each CDD scheme and to minimize the complexity of the implementation.
An aspect of the present invention for solving the above problems is to provide a method of selecting a precoding matrix that can simplify the implementation while obtaining sufficient frequency diversity gain in various channel environments according to each transmission mode. .
In addition, an aspect of the present invention is to provide a method for efficiently transmitting and receiving a signal between the transmitting and receiving terminals according to the CDD method using the precoding matrix selected as described above.
One aspect of the present invention for solving the above problems provides a method for a user equipment (UE) to receive a signal in an openloop spatial multiplexing (SM) transmission mode. The method includes receiving a rank indicator (RI) and antenna number information from a base station; And when the number of transmit antennas is 2, signal transmission of the base station is performed by a first matrix W corresponding to an identity matrix, a second matrix D corresponding to a diagonal matrix, and a unitary matrix. Estimating that the third matrix U corresponding to is transmitted through precoding by a matrix WDU multiplied sequentially; And receiving a signal according to the estimation of the estimating step. In this case, when the rank indicator is greater than 1, the method may further include estimating that the signal transmission of the base station is performed according to a cyclic delay diversity (CDD) scheme.
Meanwhile, another aspect of the present invention provides a method for transmitting a signal by a base station in an openloop spatial multiplexing (SM) transmission mode. The method includes transmitting a signal according to a cyclic delay diversity (CDD) scheme when the transmission rank is greater than 1, wherein the transmitting signal is a transmission signal when the number of transmission antennas is two. Is sequentially multiplied by a first matrix W corresponding to an identity matrix, a second matrix D corresponding to a diagonal matrix, and a third matrix U corresponding to a unitary matrix. Performing precoding by matrix (WDU); And mapping the precoded signal to a resource element and transmitting the same.
In such embodiments, when the number of transmit antennas is 2 and the rank according to the rank indicator RI is 2, the second matrix D may have a form of 2 * 2. In addition, in the openloop SMx transmission mode, the base station uses the first matrix W,
It is preferable that the user equipment does not feed back a precoding matrix index (PMI) to the base station.
Meanwhile, in the abovedescribed embodiments, when the base station transmits signals in the open loop spatial multiplexed transmission mode, when the number of transmit antennas is 2 and the transmission rank is 2, the transmission signals are transmitted according to a cyclic delay diversity (CDD) scheme. Precoding is performed by performing a precoding by a matrix DU, in which the first matrix D corresponding to the diagonal matrix and the second matrix U corresponding to the unitary matrix are sequentially multiplied, thereby precoding the precoded signal. It can also be seen as mapping and transmitting resource elements.
According to each embodiment of the present invention as described above, it is possible to simplify the implementation while obtaining a sufficient diversity gain for each transmission mode.
Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description, together with the accompanying drawings, is intended to illustrate exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. For example, the following description is given by way of specific examples applied to 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) system for the sake of understanding, but the present invention is not limited to any 3GPP LTE system as well as a general multiantenna system. The same principle can be applied to a wireless communication system. In addition, in the following description, the base station may be replaced with other terms such as "Node B" and "eNode B", and the terminal may be replaced with terms such as "user equipment" (UE) and "mobile station (MS)". Can be applied.
The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. In some instances, wellknown structures and devices are omitted or shown in block diagram form around the core functions of each structure and device in order to avoid obscuring the concepts of the present invention. In the following description, the same components are denoted by the same reference numerals throughout the specification.
As described above, in one aspect of the present invention, a precoding matrix can be selected that can simplify the implementation while obtaining sufficient frequency diversity gain in various channel environments according to each transmission mode, and efficiently transmit and receive signals using the same. To provide a method. To this end, in the following, the downlink of the 3GPP LTE system described above will be described in detail for each transmission mode. Based on this, for example, the precoding matrix can be efficiently configured in the open loop spatial multiplexing transmission mode. The method of transmitting and receiving signals according to the CDD method will be described. However, the downlink of the 3GPP LTE system is exemplary only, and the present invention may be applied to other wireless communication situations.
5 is a conceptual diagram schematically illustrating a transmission process of a downlink physical channel in a 3GPP LTE system.
The codeword generated through the channel coding is performed before scrambling 501 to generate a scrambled bit block. The bit block thus generated is then generated as a modulation symbol modulated by QPSK, 16 QAM or 64 QAM by modulation mapper 502. Meanwhile, the symbols thus modulated are mapped to one or more layers by the layer mapper 503. In the 3GPP LTE system, up to two codewords can be transmitted at the same time. The two codewords are mapped to four or less layers according to predetermined criteria.
As such, precoding 504 is performed on the symbols on which the layer mapping is completed. Precoding 504 includes (1) precoding for spatial multiplexing (SM), and (2) precoding for spatial transmission diversity, and precoding for spatial multiplexing ( There is a) precoding for spatial multiplexing (SM) without the application of CDD, and (b) precoding for large delay CDD (Large Delay CDD). In the case of the openloop spatial multiplexing transmission mode, when the transmission rank is greater than 1, the base station transmits a signal according to the CDD based precoding scheme. In addition, in a system having 2 transmit antennas (2 Tx systems), a signal is transmitted through precoding based on a fixed specific precoding matrix. In a system having 4 transmit antennas (4 Tx systems), a base station is assigned to each resource element. Signals can be transmitted by applying different precoding schemes cyclically.
Such precoded transmission symbols are mapped to appropriate resource elements by the resource element mapper 505 and then transmitted via the transmit antenna via the OFDM signal generator 506.
Meanwhile, in the precoding scheme for spatial multiplexing among the abovedescribed precoding schemes, a scheme for reducing signaling overhead by using a specific precoding matrix in a predetermined codebook between transmitting and receiving sides is used, and among them, a precoding scheme for a large delay CDD is particularly used. The coding scheme will be described in more detail below. In addition, in the following description, precoding for a large delay CDD may be referred to as “CDD based precoding”, “CDD based precoding” or “phase shift based precoding” unless there is confusion.
CDD base Precoding Basic structure DU rescue
Phase shift based precoding transmits all streams to be transmitted through the entire antenna, but multiplies the sequences of different phases. In general, when the phase sequence is generated using the cyclic delay value, the channel size becomes larger or smaller depending on the frequency domain while generating frequency selectivity in the channel when viewed from the receiver.
The phase shift based precoding matrix P can be expressed as follows.
Here, k denotes a resource index, and for example, indicates an index of a subcarrier or a virtual timefrequency resource or an index of a specific frequency band.
( i = 1, ..., N _{t} , j = 1, ..., R) represents the complex weight determined by k. In addition, N _{t} represents the number of transmit antennas, and R represents the spatial multiplexing rate. Here, the complex weight may have a different value depending on the OFDM symbol multiplied by the antenna and the index of the corresponding subcarrier. The complex weight may be determined according to at least one of channel conditions and presence or absence of feedback information.Meanwhile, the precoding matrix P of Equation 1 is preferably designed to reduce the channel capacity loss in the multiantenna system. To this end, the channel capacity of a multiantenna openloop system is expressed as follows.
Here, H is a multiantenna channel matrix of size N _{r} x N _{t} and N _{r} represents the number of receiving antennas. Applying the phase shift based precoding matrix P as shown in Equation 1 to Equation 2 is as follows.
As shown in Equation 3, in order to avoid loss in channel capacity, PP ^{H} must be an identity matrix, so it is preferable that the phase shift based precoding matrix P satisfies the following conditions.
That is, the phase shift based precoding matrix P is preferably based on the unitary matrix.
The abovedescribed phase shift based precoding matrix is expressed as shown in Equation 5 below for a system having an antenna number N _{t} (N _{t} is a natural number of 2 or more) and a spatial multiplexing rate R (R is a natural number of 1 or more). Can be. Since this can be seen as a generalized representation of the conventional phase shift diversity scheme, the multiantenna technique according to Equation 5 will be referred to as generalized phase shift diversity (GPSD).
here,
Denotes the GPSD matrix for the kth resource index of the MIMOOFDM signal having N _{t} transmit antennas and a spatial multiplexing rate of R, The It is a unitary matrix (second matrix) that satisfies Δ is used to minimize interference between subcarrier symbols corresponding to each antenna. In particular, in order to maintain the unitary matrix characteristic of the diagonal matrix (first matrix; D) for phase shifting, It is desirable that the self also satisfies the condition of the unitary matrix.In Equation 5, the phase angles θ _{i} , i = 1, ..., N _{t} in the frequency domain have the following relationship with the delay time τ _{i} , i = 1, ..., N _{t} in the time domain.
Here, N _{fft} represents the number of subcarriers of the OFDM signal.
As shown in Equation 5, the precoding matrix defined in the form of the product of the first matrix corresponding to the diagonal matrix D and the second matrix corresponding to the unitary matrix U is hereinafter referred to as "CDDbased precoding. It will be referred to as the "basic structure" or "DU structure".
Generalized Phase Transition Diversity expansion  PDU Of WDU rescue
In the abovedescribed embodiment of the DU structure, a matrix P corresponding to a precoding matrix selected from a predetermined codebook between the transmitting and receiving sides is included in the basic structure of the CDD based precoding composed of the diagonal matrix D and the unitary matrix U. In addition, extended CDDbased precoding matrices can be constructed. This can be expressed as follows.
The extended CDDbased precoding matrix is characterized in that a precoding matrix P having a size of N _{t} x R is added before the diagonal matrix, and thus the size of the diagonal matrix is changed to R x R, compared to Equation 5. . The added precoding matrix (
) May be set differently for a specific frequency band or a specific subcarrier symbol, and it is preferable that the open loop system is set to use a fixed specific matrix as described above. Such a precoding matrix ( In addition, a more optimized signaltonoise ratio (SNR) gain can be obtained.In addition, the added precoding matrix may be designated as "W" as a matrix selected from the codebook of the 3GPP LTE system.
Hereinafter, as described above, the extended CDDbased precoding matrix will be referred to as a "PDU structure" or "WDU" structure.
Codebook subset restriction technique
In the 3GPP LTE system, a codebook preset between a transmitting and receiving end is as follows for 2 Tx and 4 Tx.
Table 1 shows a codebook used in a 2 Tx system, and Table 2 shows a codebook used in a 4 Tx system.
Meanwhile,
There may be a case in which a codebook including two precoding matrices is used by applying a codebook subset restriction scheme using only a portion of a codebook according to a base station or a terminal. in this case, Precoding matrices It can be shortened to the number of precoding matrices. Here, the codebook subset limiting technique may be used to reduce multicell interference or to reduce complexity. here Assume that the conditions of For example, the total number of precoding matrices in a codebook Is a complete set of codebooks And, for example, a codebook determined to use only four precoding matrices out of six precoding matrices Can be expressed as Equation 8 below.
In Equation (8)
The Equivalent codebook that rearranges the index of the codebook.Meanwhile, if a precoding matrix set defined in a transmission / reception period at a specific time is defined in advance, it may be expressed as in Equation (9).
In Equation 9, the set of precoding matrices is
It contains two precoding matrices. Equation 9 above may be simplified to a form as shown in Equation 10 below.
That is, Equations 8 and 9 represent codebooks.
The precoding matrices within the loop are repeatedly used according to subcarriers or resource indexes. And, in Equation 10 above Is a mix of data streams, May be referred to as a data stream substitution matrix and may be selected according to the spatial multiplexing rate R as shown in Equation 9. Can be expressed in a simple form as shown in Equation 11 below.
Spatial Multiplexing Rate 3
Spatial Multiplexing Rate 4
The method of cyclically repeating the precoding matrices in the abovedescribed codebook may be used in the codebook to which the codebook restriction technique is applied. For example, the equation
Applying Equation 10 may be expressed as Equation 12 below.
K in Equation 12 above represents a resource index and
to be. That is, Equation 12 represents a codebook in which the precoding matrix is limited. The precoding matrices within the loop are repeatedly used according to subcarriers or resource indexes.On the other hand, in the case of performing CDD based precoding using the full rank in the 2 Tx system using the open loop spatial multiplexing transmission mode as described above, since the sufficient frequency diversity gain can be obtained due to the large delay CDD itself, It is preferable to fix the coding matrix W to any one because it can simplify the implementation. Therefore, in the following embodiments, a method of selecting a preferred precoding matrix when performing CDD based precoding based on the fixed precoding matrix will be described.
Open loop Spatial multiplexing In mode CDD base Precoding Way
Large delay CDD precoding in the open loop SM mode may be performed according to the PDU structure or the WDU structure as shown in Equation 7 above. In order to explain the abovedescribed circular application concept, it is expressed as follows.
here,
Represents the number of precoding matrices in the codebook subset, Denotes the number of consecutive resource elements RE using the same precoding matrix, and i denotes the resource index as k. Therefore, the precoding matrix is Are used per resource index, Precoding matrices may be used cyclically. Further details on the openloop large delay CDD scheme are as follows.(1) The precoding matrix index (PMI) is not used.
(2) in 2 Tx system
Is set to one.(3) in 4 Tx system
Is set to 4, and regardless of the rank, {12, 13, 14, 15} of Table 2 is used.(4) The open loop large delay CDD scheme is applied only when the rank is larger than one, and the transmit diversity scheme is used for the rank one.
(5) Dynamic rank adaptation is possible between the transmit diversity scheme and the open loop SM scheme.
In the case of a 4 Tx antenna, only four of the sixteen matrices defined in Table 2 above are used, regardless of rank, to obtain sufficient diversity gain while reducing decoding complexity. However, in the case of the 2 Tx open loop SM, only one of three matrices for rank 2 is used in Table 1 above. Therefore, it is very important to correctly select a matrix used in such a case, and this embodiment proposes a method of selecting a precoding matrix for large delay CDD based precoding in the 2 Tx open loop SM scheme.
First, considering the case of rank 2 in Table 1 as follows.
In Equation 14, when the index 1 and the index 2 are combined with a large delay CDD, a similar function is performed as an identity matrix for performing column switching. However, when the index 0 precoding matrix is used for large delay CDD based precoding, the open loop SM functions as a DFT matrix for performing heat exchange, thereby obtaining a higher SNR gain in a good correlation channel. Can be. Accordingly, in a preferred embodiment of the present invention, the first matrix W and the diagonal matrix corresponding to the unit matrix of index 0 in Equation 14 above are precoded when the rank is 2 in the openloop spatial multiplexed transmission mode 2 Tx. It is proposed to transmit a signal by performing precoding by a matrix (WDU or PDU) that is sequentially multiplied by a second matrix D corresponding to and a third matrix U corresponding to a unitary matrix. When the matrix of index 0 is used as the first matrix W, the present inventors performed a simulation as follows about what performance difference is shown compared to the case of using the index 1 or 2.
<Simulation Result>
As described above, in the case of using index 1 of Equation 14 and index 2 in openloop CDDbased precoding, similar performances are shown. In the present simulation, W in the WDU structure is represented by index 0 of Equation 14. The comparison is made only for the case of using the index and the case of using the index 1. In this simulation, we compared the performance of 2 Tx open loop SM according to rank 2 matrix index, MCS level and channel mode. In addition, it is assumed that a high time varying channel is generally used for longterm link adaptation of a distributed transmission mode to provide robustness under a fast channel update environment. Table 3 below shows the remaining assumptions of this link level simulation.
FIG. 6 is a graph comparing performance when using index 0 and index 1 for rank 2 of a 2 Tx codebook for an open loop SM under an ITUPedA channel.
As can be seen from FIG. 6, it can be seen that the use of index 0 and the use of index 1 in an uncorrelated spatial channel do not show much difference in performance. However, under a high correlation channel, it can be seen that the use of index 0 for rank 2 of the 2 Tx codebook shows a significant performance improvement over the case of using index 1 according to the present embodiment. This can be seen because the DFT matrix forms a beam and provides an SNR gain by averaging the two beams. In addition, when a high modulation level is used, it can be confirmed that the use of index 0 for rank 2 of the 2 Tx codebook shows higher performance improvement according to the present embodiment.
FIG. 7 is a graph comparing performance when using index 0 and index 1 corresponding to rank 2 in a 2 TX codebook for an open loop SM under a 6Ray TU channel.
That is, FIG. 7 shows a performance comparison similar to that of FIG. 6 except for the channel mode. As can be seen from FIG. 7, it can be seen that the use of index 0 according to the present embodiment provides a better performance gain even under a rich frequency diversity channel.
The above description is summarized as a method for receiving a signal from a base station by a terminal in one aspect of the present invention. In the open loop spatial multiplexing transmission mode, when the terminal receives a signal, the terminal first receives a rank indicator (RI) from the base station through downlink control information. If the received rank indicator is 1, the UE transmits a signal according to the transmit diversity scheme, and if the rank indicator is greater than 1, the UE assumes that the base station transmits a signal according to the CDD scheme.
If the rank indicator is greater than 1, that is, the base station transmits a signal according to the CDD scheme, the reception scheme may vary depending on the case where the number of transmission antennas is two and four. In the case of 4 Tx, the UE estimates that precoding is performed by cyclically applying four precoding matrices of the 16 codebooks to P or W of the PDU / WDU structure as described above, and receives a signal. Meanwhile, in the case of 2 Tx, the UE estimates that the base station performs precoding by applying the unit matrix corresponding to index 0 of Equation 14 to P or W of the PDU / WDU structure and receives a signal. According to the estimation result, the terminal receives a signal.
In the case of 2 Tx rank (R) 2 of the above scheme, the diagonal matrix portion of the PDU / WDU structure has a 2 * 2 form. That is, since the unit matrix is used as "P" or "W" in the PDU / WDU structure, and the number of transmit antennas and the number of ranks are the same, the CDDbased precoding base matrix or the DU structure of the abovedescribed embodiments is substantially the same. It can also be seen as an application.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The foregoing description of preferred embodiments of the invention disclosed herein has been presented to enable any person skilled in the art to make and use the invention. While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims It can be understood that Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
According to the signal transmission / reception method according to each embodiment of the present invention as described above, it is possible to efficiently select the precoding matrix according to each transmission mode to obtain a sufficient diversity gain, so as not to complicate the implementation. This approach can be applied according to the same principle to the abovementioned 3GPP LTE system as well as any multiantenna communication system using CDD based precoding.
1 is a diagram illustrating a general structure of a multiantenna transmission and reception system using OFDM.
2 illustrates a configuration of a transmitting end of a multiple antenna system using a CDD technique.
FIG. 3 is a diagram for describing a method of implementing the CDD technique in the frequency domain as shown in FIG. 2.
4 is a block diagram of a transmitter / receiver of a multiantenna system using codebook based precoding.
5 is a conceptual diagram schematically illustrating a transmission process of a downlink physical channel in a 3GPP LTE system.
FIG. 6 is a graph comparing performance when using index 0 and index 1 for rank 2 of a 2 Tx codebook for an open loop SM under an ITUPedA channel.
FIG. 7 is a graph comparing performance when using index 0 and index 1 corresponding to rank 2 in a 2 TX codebook for an open loop SM under a 6Ray TU channel.
Claims (12)
 A method for receiving a signal by a user equipment (UE) in an openloop spatial multiplexing (SM) transmission mode,Receiving the number information of the transmit antennas from the base station; AndAssuming that a precoded signal is transmitted using a matrix for transmitting a signal in an openloop spatial multiplexing (SM) mode of a transmitting antenna, receiving a signal from the base station Including,The matrix is a matrix WDU in which the first matrix W, the second matrix D corresponding to the diagonal matrix, and the third matrix U corresponding to the unitary matrix are sequentially multiplied.The user equipment determines that the base station using the openloop spatial multiplexing mode of the two transmit antennas uses the first matrix W in the matrix as a unitary matrix for large delay delay cyclic delay diversity (CDD) based precoding. Characterized in that it is assumed to use a fixed identity matrix),How to receive the signal.
 The method of claim 1,The second matrix D isWhen the number of transmit antennas is 2 and the transmission rank (Rank) is 2, it has a 2 * 2 form, the signal receiving method.
 The method of claim 1,The user device,In an openloop SM multiplex mode of the two transmit antennas, the base station decodes the first matrix W of the matrix for the large delay CDD precoding. Assume that it is fixed to use,And the user equipment does not feed back a precoding matrix index (PMI) to the base station.
 In a method for transmitting a signal by a base station in an openloop spatial multiplexing (SM) transmission mode,Precoding a signal using a matrix for large delay cyclic delay diversity (CDD) based precoding in an open loop spatial multiplexing mode of a two transmit antenna;Mapping the precoded signal to resource elements; AndTransmitting the mapped signal to a user equipment (UE);The matrix is a matrix WDU in which the first matrix W, the second matrix D corresponding to the diagonal matrix, and the third matrix U corresponding to the unitary matrix are sequentially multiplied.The base station using the openloop spatial multiplexing mode of the two transmit antennas is characterized in that the first matrix (W) in the matrix is fixed to use an identity matrix for large delay CDD based precoding. ,Signal transmission method.
 5. The method of claim 4,The second matrix D isWhen the number of transmit antennas is 2 and the transmission rank (Rank) is 2, it has a 2 * 2 form.
 A user equipment (UE) for receiving a signal from a base station in a wireless communication system,A precoded signal was transmitted using a matrix for receiving information on the number of transmit antennas from the base station and transmitting a signal in an openloop spatial multiplexing (SM) mode of two transmit antennas. A receiving module for receiving a signal from the base station assuming;The matrix is a matrix WDU in which the first matrix W, the second matrix D corresponding to the diagonal matrix, and the third matrix U corresponding to the unitary matrix are sequentially multiplied.The user equipment determines that the base station using the openloop spatial multiplexing mode of the two transmit antennas uses the first matrix W in the matrix as a unitary matrix for large delay delay cyclic delay diversity (CDD) based precoding. Characterized in that it is assumed to use a fixed identity matrix),User device.
 The method of claim 7, whereinThe second matrix D isIf the number of the transmission antenna is 2 and the transmission rank (Rank) is 2, the user device having a form of 2 * 2.
 The method of claim 7, whereinThe user device,In an openloop SM multiplex mode of the two transmit antennas, the base station decodes the first matrix W of the matrix for the large delay CDD precoding. Assume that it is fixed to use,The user equipment does not feed back a precoding matrix index (PMI) to the base station.
 A base station for transmitting a signal to a user equipment (UE) in a wireless communication system,A precoder for precoding a signal using a matrix for large delay Large Delay cyclic delay diversity (CDD) based precoding in an openloop spatial multiplexing (SM) mode of two transmit antennas;A mapper for mapping the precoded signal to resource elements; AndA transmitting module for transmitting the mapped signal to the user equipment,The matrix is a matrix WDU in which the first matrix W, the second matrix D corresponding to the diagonal matrix, and the third matrix U corresponding to the unitary matrix are sequentially multiplied.The base station using the openloop spatial multiplexing mode of the two transmit antennas is characterized in that the first matrix (W) in the matrix is fixed to use an identity matrix for large delay CDD based precoding. ,Base station.
 11. The method of claim 10,The second matrix D isWhen the number of transmit antennas is 2 and the transmission rank (Rank) is 2, the base station having a 2 * 2 form.
Priority Applications (3)
Application Number  Priority Date  Filing Date  Title 

US3647508P true  20080314  20080314  
US61/036,475  20080314  
KR1020080080461A KR101328961B1 (en)  20080314  20080818  Method For Transmitting And Receiving Signals In OpenLoop Spatial Multiplexing Mode 
Applications Claiming Priority (7)
Application Number  Priority Date  Filing Date  Title 

KR1020080080461A KR101328961B1 (en)  20080314  20080818  Method For Transmitting And Receiving Signals In OpenLoop Spatial Multiplexing Mode 
CN 200980115957 CN102017449B (en)  20080314  20090122  Method for transmitting and receiving signals in openloop spatial multiplexing mode 
PCT/KR2009/000335 WO2009113766A1 (en)  20080314  20090122  Method for transmitting and receiving signals in openloop spatial multiplexing mode 
JP2010550586A JP5236753B2 (en)  20080314  20090122  Signal transmission and reception method in open loop spatial multiplexing mode 
EP09718805.6A EP2272180B1 (en)  20080314  20090122  Method for transmitting and receiving signals in openloop spatial multiplexing mode 
ES09718805.6T ES2525338T3 (en)  20080314  20090122  Procedure for transmitting and receiving signals in open loop spatial multiplexing mode 
US12/382,366 US8320488B2 (en)  20080314  20090313  Method for transmitting and receiving signals in openloop spatial multiplexing mode 
Publications (2)
Publication Number  Publication Date 

KR20090098643A KR20090098643A (en)  20090917 
KR101328961B1 true KR101328961B1 (en)  20131113 
Family
ID=41065400
Family Applications (1)
Application Number  Title  Priority Date  Filing Date 

KR1020080080461A KR101328961B1 (en)  20080314  20080818  Method For Transmitting And Receiving Signals In OpenLoop Spatial Multiplexing Mode 
Country Status (7)
Country  Link 

US (1)  US8320488B2 (en) 
EP (1)  EP2272180B1 (en) 
JP (1)  JP5236753B2 (en) 
KR (1)  KR101328961B1 (en) 
CN (1)  CN102017449B (en) 
ES (1)  ES2525338T3 (en) 
WO (1)  WO2009113766A1 (en) 
Families Citing this family (22)
Publication number  Priority date  Publication date  Assignee  Title 

KR101527009B1 (en) *  20080711  20150618  엘지전자 주식회사  A method for multicell mimo under multi cell environment 
US20100034310A1 (en) *  20080808  20100211  Samsung Electronics Co., Ltd.  Transmit diversity schemes in OFDM systems 
US8848603B2 (en) *  20090622  20140930  Qualcomm Incorporated  Precoding control channels in wireless networks 
CN105119642B (en) *  20090927  20180720  Lg电子株式会社  Receive the method and apparatus of channel quality indicator 
CN102088340B (en) *  20100111  20130417  电信科学技术研究院  Method and device of multiaerial system for transmitting and receiving information 
KR20120003781A (en) *  20100705  20120111  주식회사 팬택  Transmitter and communicating method thereof, receiver, communicating method thereof 
US20120039402A1 (en) *  20100810  20120216  Samsung Electronics Co. Ltd.  Multiple input multiple output communication system using at least two codebooks 
EP3352380B1 (en) *  20101004  20190828  Samsung Electronics Co., Ltd.  Method and apparatus for transmitting and receiving codebook subset restriction bitmap 
JP5578617B2 (en)  20101018  20140827  パナソニック インテレクチュアル プロパティ コーポレーション オブ アメリカＰａｎａｓｏｎｉｃ Ｉｎｔｅｌｌｅｃｔｕａｌ Ｐｒｏｐｅｒｔｙ Ｃｏｒｐｏｒａｔｉｏｎ ｏｆ Ａｍｅｒｉｃａ  Transmission method, transmission device, reception method, and reception device 
WO2012108912A1 (en) *  20110207  20120816  Intel Corporation  Cophasing of transmissions from multiple infrastructure nodes 
WO2012109945A1 (en) *  20110214  20120823  中兴通讯股份有限公司  Method and system for precoding open loop spatial multiplexing and precoding indication method 
JP5991572B2 (en) *  20110228  20160914  サン パテント トラスト  Transmission method and transmission apparatus 
JP6026082B2 (en) *  20110405  20161116  シャープ株式会社  Terminal, base station, communication method and integrated circuit 
CN103812617B (en) *  20121113  20170322  上海贝尔股份有限公司  Method, device and base station for improving user equipment initial access delay 
WO2014113938A1 (en) *  20130123  20140731  Telefonaktiebolaget L M Ericsson (Publ)  Radio base station and method for precoding signal 
US9294172B2 (en) *  20130125  20160322  Lg Electronics Inc.  Method and apparatus for reporting downlink channel state 
US9712219B2 (en)  20130219  20170718  Lg Electronics Inc.  Method for transmitting signal in multiantenna wireless communication system and apparatus for the same 
GB2514111A (en)  20130513  20141119  British Broadcasting Corp  Transmission techniques 
BR112015029739A2 (en)  20130604  20170725  Huawei Tech Co Ltd  method for transmitting 4 antenna precoding array, user equipment and base station 
RU2639949C2 (en)  20130605  20171225  Эл Джи Электроникс Инк.  Method and device for transmitting channel state information in wireless communication system 
CN105493459A (en) *  20130822  20160413  Lg电子株式会社  Method and device for transmitting data by using spatial modulation scheme in wireless access system 
US20180026694A1 (en) *  20150213  20180125  Lg Electronics Inc.  Method and apparatus for communication based on common feedback information in multiple antenna system 
Citations (2)
Publication number  Priority date  Publication date  Assignee  Title 

WO2006130541A2 (en)  20050531  20061207  Qualcomm Incorporated  Rank stepdown for mimo systems employing harq 
WO2007051208A2 (en)  20051028  20070503  Qualcomm Incorporated  Unitary precoding based on randomized fft matrices 
Family Cites Families (7)
Publication number  Priority date  Publication date  Assignee  Title 

US8073068B2 (en) *  20050822  20111206  Qualcomm Incorporated  Selective virtual antenna transmission 
US8116267B2 (en) *  20060209  20120214  Samsung Electronics Co., Ltd.  Method and system for scheduling users based on userdetermined ranks in a MIMO system 
TWI343200B (en) *  20060526  20110601  Lg Electronics Inc  Method and apparatus for signal generation using phaseshift based precoding 
KR20070113967A (en) *  20060526  20071129  엘지전자 주식회사  Phase shift based precoding method and tranceiver supporting the same 
US7944985B2 (en) *  20060824  20110517  Interdigital Technology Corporation  MIMO transmitter and receiver for supporting downlink communication of single channel codewords 
JP4594361B2 (en) *  20060831  20101208  三星電子株式会社Ｓａｍｓｕｎｇ Ｅｌｅｃｔｒｏｎｉｃｓ Ｃｏ．，Ｌｔｄ．  Data transmitting / receiving apparatus and method in multiantenna system and system supporting the same 
US8160177B2 (en) *  20070625  20120417  Samsung Electronics Co., Ltd.  Transmit methods with delay diversity and spacefrequency diversity 

2008
 20080818 KR KR1020080080461A patent/KR101328961B1/en active IP Right Grant

2009
 20090122 CN CN 200980115957 patent/CN102017449B/en active IP Right Grant
 20090122 WO PCT/KR2009/000335 patent/WO2009113766A1/en active Application Filing
 20090122 ES ES09718805.6T patent/ES2525338T3/en active Active
 20090122 JP JP2010550586A patent/JP5236753B2/en active Active
 20090122 EP EP09718805.6A patent/EP2272180B1/en active Active
 20090313 US US12/382,366 patent/US8320488B2/en active Active
Patent Citations (2)
Publication number  Priority date  Publication date  Assignee  Title 

WO2006130541A2 (en)  20050531  20061207  Qualcomm Incorporated  Rank stepdown for mimo systems employing harq 
WO2007051208A2 (en)  20051028  20070503  Qualcomm Incorporated  Unitary precoding based on randomized fft matrices 
Also Published As
Publication number  Publication date 

US20100166094A1 (en)  20100701 
EP2272180A4 (en)  20131016 
US8320488B2 (en)  20121127 
EP2272180A1 (en)  20110112 
JP2011518458A (en)  20110623 
CN102017449B (en)  20130911 
ES2525338T3 (en)  20141222 
KR20090098643A (en)  20090917 
CN102017449A (en)  20110413 
JP5236753B2 (en)  20130717 
WO2009113766A1 (en)  20090917 
EP2272180B1 (en)  20141022 
Similar Documents
Publication  Publication Date  Title 

KR101314423B1 (en)  Method and apparatus for implementing space frequency block coding in an orthogonal frequency division multiplexing wireless communication system  
TWI376898B (en)  
US9544093B2 (en)  Method and apparatus for combining spacefrequency block coding, spatial multiplexing and beamforming in a MIMOOFDM system  
US9258041B2 (en)  Methods and systems for combined cyclic delay diversity and precoding of radio signals  
ES2663273T3 (en)  Method to transmit data in a multiantenna system  
US8218663B2 (en)  Reference signal resource allocation for single user MIMO  
CN101682380B (en)  Multiuser mimo feedback and transmission in a wireless communication system  
RU2566255C2 (en)  System and method for pucch subband feedback signalling in wireless network  
EP2424123B1 (en)  Apparatus and method for transmitting a reference signal in a wireless communication system  
EP1973284B1 (en)  Efficient joint transmission of different control information in a wireless communications system  
EP2119036B9 (en)  Data transmitting and receiving method using phase shift based precoding and transceiver supporting the same  
JP5023153B2 (en)  Phase transition based precoding method and transceiver supporting the same  
KR100895992B1 (en)  Apparatus and method for increasing the number of antennas in wireless communication system using multiple antennas  
CA2729577C (en)  Methods and apparatus using precoding matrices in a mimo telecommunications system  
CN105187101B (en)  The method and apparatus of effective Feedback in the wireless communication system for supporting mutiple antennas  
JP6279633B2 (en)  Codebook subset limited bitmap transmission / reception method and apparatus  
DK2232726T3 (en)  Open loop precycling by MIMO communication  
KR20110009025A (en)  Method and apparatus for transmitting uplink control information  
JP4987077B2 (en)  Error correction method and apparatus in multiple subcarrier communication system using multiple antennas  
RU2421930C2 (en)  Method of transfer using preliminary coding based on phase shift and device for its realisation in wireless communication system  
EP1780925A2 (en)  Multiple antenna communication system using spatial precoding  
EP2156588B1 (en)  Cdd precoding for an open loop sumimo system  
JP2011525321A (en)  System and method for SCFDMA transmission diversity  
JP5149257B2 (en)  Wireless communication system, communication apparatus, and wireless communication method  
CA2655757C (en)  Method for reducing feedback information overhead in precoded mimoofdm systems 
Legal Events
Date  Code  Title  Description 

A201  Request for examination  
E701  Decision to grant or registration of patent right  
GRNT  Written decision to grant 